Shadow defence secretary Jim Murphy has refused to publicly retract his comments about the Unite union, which he made amid the Falkirk candidacy fix row.
Fellow Labour MP Tom Watson earlier demanded Mr Murphy withdraw his claim that Unite had "well and truly overstepped the mark" with "external interference".
But, responding on Twitter after an internal inquiry cleared the union, Mr Murphy tweeted:
@tom_watson You know how to get in touch away from Tory twitter eyes m'while I'll just get on with supporting Ed's plans for Party/TU reform
More top news
The coup shows a split in the cabinet between ministers who want to stop a no-deal Brexit, and those who want to prevent a referendum.
Speculation that the PM will be ousted from Downing Street has reached fever pitch.
Newly-released papers show a young David Cameron condemning ‘Euro red tape’ while working as a researcher for the Conservative Party in 1988